Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 4 - Section 4.5 - Exponential and Logarithmic Functions - 4.5 Exercises - Page 368: 21

Answer

$x=-\dfrac{\ln2-1}{4}\approx0.076713$

Work Step by Step

$e^{1-4x}=2$ Apply $\ln$ to both sides of the equation: $\ln e^{1-4x}=\ln2$ Take down the exponent $(1-4x)$ to multiply in front of its respective $\ln$: $(1-4x)\ln e=\ln2$ Since $\ln e=1$, the equation becomes: $1-4x=\ln2$ Solve for $x$: $-4x=\ln2-1$ $x=-\dfrac{\ln2-1}{4}\approx0.076713$
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